| Global warming is the most serious problem facing human society,for the realization of the 3060 plan,the offshore wind farm has been in the large-scale development stage,with the development of the offshore wind farm technology mature,wind power will become a important source of energy for the sustainable development of China’s eastern coastal areas,but the liquid water content in the air,by sea in winter temperature is reduced,Wind turbines encounter icing,which will reduce the power generation of wind turbines and also make the operating wind turbines face the safety problems of icing on blades,nacelles and measuring instruments.In this paper,the blade of NREL 5MW offshore wind turbine is taken as the research object to study the change of lift drag coefficient of the airfoil after the blade freezes and the influence of the blade freezes on its aerodynamic performance.The FENSAP-ICE software is used to obtain the simulated icing blade model.It is applied to CFD engineering applications,and the aerodynamic performance of airfoils and wind turbine blades is sorted out through analysis and research.The main research contents and achievements of this paper include:The influence of icing conditions on the aerodynamic performance of airfoil before and after icing is studied.Will first NREL single only 5 MW wind turbine blade was simulated freezing experiment,respectively controlling environmental temperature and liquid water content and variable parameters such as flow velocity in FENSAP-ICE freezes software simulating experiment,the results show that liquid water content in the air changes impact on blade icing difference,the biggest airfoil shape change is most obvious,Of tip three airfoil section(DU25 DU21 NACA64)were analyzed,and the lift-to-drag ratio of three groups of airfoil ice accretion and the pressure distribution and flow chart,great changes have three kinds of lift coefficient under different working conditions are reduced,drag coefficient increases,the maximum lift coefficient reduced by 28% after DU25 airfoil ice,resistance coefficient of the overall rise,A maximum increase of 31%;When the Angle of attack is 15°,the lift coefficient of DU21 airfoil decreases by 33% and the drag coefficient increases by30%.After freezing,the lift coefficient of NACA64 airfoil begins to decline significantly when the Angle of attack is around 6°,and drops about 14% when the Angle of attack is 12°.The drag coefficient curve remains consistent with the overall upward trend of the original,rising 6% when the Angle of attack is-5°,and 7% when the Angle of attack is 15°.Under three different environment variables,DU25 airfoil flow field structure change in the ice,with the increase of liquid water content,flow velocity,environmental temperature,freezing airfoil trailing edge generate more obvious separation of airfoil stall condition is more serious,frozen airfoil ice quantity is big,the leading edge front part form small eddy,The eddies at the trailing edge gradually became larger,and even three eddies appeared.Compared with the trailing edge separation zone formed on the surface of the original airfoil,the change of separation zone changed the aerodynamic characteristics of the airfoil,and the aerodynamic performance decreased seriously.The change of flow field structure of DU21 airfoil is not as obvious as that of DU25 airfoil.The effect of icing on the flow field around the airfoil is not significant,but the separation phenomenon at trailing edge of the frozen airfoil is still earlier and the separation area is larger than that of the original airfoil.The flow field structure of NACA64 airfoil changes little before and after freezing,and the influence can be almost ignored.Under the three variables,no vortex is formed at the leading edge of freezing,and the vortex change at the trailing edge is not obvious.Compared with the original airfoil,the flow field structure only changes slightly,indicating that icing has little influence on the flow field structure of NACA64 airfoil.Blade icing changes the wind turbine power,spindle speed,power generation and other parameters.The most obvious power loss is caused by the change of liquid water content,and the most serious loss is 35% when the rated wind speed is 11m/s.The frozen wind turbine power was reduced by 17% at the spindle speed of 11.4m/s due to the change of liquid water content.An unfrozen 5MW wind turbine generates 5,000 kw per hour,but the frozen wind turbine generates 4,695 kw per hour due to the influence of liquid water content.Therefore,due to the influence of icing,the power generation loss of the wind turbine will increase gradually over time,with the maximum loss of 7%.Research work of this paper belongs to the wind turbine research in the fields of ice,ice axial-flow compressor.in order to offshore wind,deicing aspects provide resources,can also design personnel in the design of related aspects,such as when maintaining provide certain help,at the same time in this paper,the method and technology of wind turbine freeze method can also be of high altitude wind writers ice problems provide some help. |
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